On vehicles having internal combustion engines, in order to reduce oxides of nitrogen (NOx) in the exhaust, it is known to produce a gaseous mixture of hydrogen and carbon monoxide (referred to hereinafter as syngas) for regeneration of adsorption material in NOx traps. The generation of syngas from engine fuel, engine exhaust and air, for use in regenerating NOx traps is disclosed in copending U.S. patent application Ser. No. 10/243,105, filed Sep. 13, 2002. Another example of such a system is illustrated in commonly owned copending U.S. patent application Ser. No. 10/309,712, filed Dec. 4, 2002.
In a prior art system shown in FIG. 1, an engine system 11 includes an internal combustion engine 12 which receives a mixture of fuel and air in a line 13. Air on a line 17 typically is provided by a turbo charger, the pressure of the air being suitably regulated by a valve 18. Fuel is provided on a line 19 from a fuel pump 20. The exhaust of the engine on a line 23 is provided through either a valve or a fixed orifice 24 to a static mixer 25 along with fuel from the line 19, which is passed through either a valve or a fixed orifice 26. The output of the static mixer on a line 29 is applied to a catalytic partial oxidizer (CPO) 30, which generates a gaseous mixture of hydrogen, carbon monoxide and other gases, all as is conventional and not relevant to the invention. The output of the CPO on a line 31 is applied to a two-way valve 33, although it could be a valve having more selections as is described elsewhere therein.
The exhaust on line 23 is also provided to syngas-utilizing apparatus, such as a set of valves 34 feeding a pair of NOx traps 35, which may be as disclosed in the aforementioned application Ser. No. 10/243,105, and may employ, for example, barium carbonate as the NOx adsorption material for reducing NOx emissions of an engine. The other input to the valves 34 is provided on a line 38 by one of the settings of the two-way valve 33. Thus, during the short period of time (5–10 seconds, typically) when the adsorbent material in one of the NOx traps is being regenerated by syngas, a signal 39 from a controller 40 will cause the two-way valve 33 to provide an effective amount of syngas to the valves 34; in this case, an effective amount is the amount needed to regenerate an NOx trap. The controller 40 switches the valves 34 back and forth by means of signals 41 so that each of the NOx traps alternatively adsorbs NOx in a larger period (typically on the order of 80–100 seconds) and then is regenerated by the syngas during the smaller period of time.
When syngas is not required, the controller 40, via the signal 39, will cause the setting of the two-way valve 33 to apply syngas to an EGR line 43 that receives exhaust through a conventional EGR valve 44 from the exhaust line 23. The EGR gas is cooled in a heat exchanger 45, passed through another conventional EGR valve 46 and thence mixed with the air/fuel mixture just before the combustion chamber of the engine 12. The EGR components 43–46 are conventional.
In the apparatus of FIG. 1, when the engine 12 is in normal operation, the CPO is allowed to function at its rated capacity, to continuously provide an effective or adequate amount of syngas. The output of the CPO is alternatively provided to the NOx traps 35 or diverted to the inlet of the engine 12. Since the heat value of the syngas is recovered in the engine, improving engine operation and reducing its unwanted emissions, the amount of fuel utilized to generate the syngas does not result in an efficiency loss of the overall engine system. By causing the CPO to operate continuously (during normal engine operation), there is no need to start up and shut down the CPO frequently; thus, the control of the CPO is simplified significantly, and the risk of damage to the CPO catalyst is minimized.
In large trucks, typically those powered with a diesel engine, the amount of electrical energy which is consumed at times requires an auxiliary power unit. Auxiliary power units currently available are very expensive, and the fuel processing systems required to power auxiliary power units is very complicated and expensive, and not practical for common use.